> On Apr 13, 2016, at 8:31 PM, Nick Coghlan <[email protected]> wrote: > >>> class Special(bytes): >>> def __fspath__(self): >>> return 'str-val' >>> obj = Special('bytes-val', 'utf8') >>> path_obj = fspath(obj, allow_bytes=True) >>> >>> With #2, path_obj == 'bytes-val'. With #3, path_obj == 'str-val'. > > In this kind of case, inheritance tends to trump protocol.
Sure, but... > example, int subclasses can't override operator.index: ... > The reasons for that behaviour are more pragmatic than philosophical: > builtins and their subclasses are extensively special-cased for speed > reasons, OK, but in this case, purity can beat practicality. If the author writes an __fspath__ method, presumably it's because it should be used. And I can certainly imagine one might want to store a path representation as bytes, but NOT want the raw bytes passed off to file handling libs. (of course you could use composition rather than subclassing if you had to) -CHB _______________________________________________ Python-Dev mailing list [email protected] https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com